1. Field of the Invention
The present invention relates generally to wireless communication technology, and more particularly, to a method and an apparatus for supporting User Equipment (UE) mobility in a wireless communication system.
2. Description of the Related Art
The structure of System Architecture Evolution (SAE) is illustrated in FIG. 1. A UE 101 is a terminal device for receiving data. An Evolved Universal Terrestrial Radio Access Network (EUTRAN) 102 is a wireless access network that includes evolved Node B (eNB), which provides the UE 101 with an interface for a wireless network. A Mobile Management Entity (MME) 103 manages a mobility context, a session context, and information about security for the UE 101. A Serving GateWay (SGW) 104 primarily offers the functions of a user plane. MME 103 and SGW 104 can be located at the same physical entity. A Local GateWay (LGW) 105 is responsible for functions such as, charging, legal interception, etc. It is possible for both the SGW 104 and the LGW 105 to be located at the same physical entity. A Policy and Charging Rules Function (PCRF) 108 provides a Quality of Service (QoS) policy and charging criterion. A Serving General Packet Radio Service (GPRS) Supporting Node (SGSN) 108 is network node equipment that provides routing for data transmission in a Universal Mobile Telecommunications System (UMTS). A Home Subscriber Server (HSS) 109 is a home subscriber sub-system, which is responsible for storing user information, such as, for example, a current location of the UE, an address of the serving node, security related information for the user, activated packet data context for the UE, etc.
Due to the increased speed of UE data services, 3rd Generation Partnership Project (3GPP) networks have been proposed that have the ability to support Selected Internet Protocol Traffic Offload (SIPTO) and Local Internet Protocol Access (LIPA). In SIPTO, when the UE accesses the Internet or an external network through a Home eNB (HeNB), a Home Node B (HNB) or an eNB/NodeB, the network can select or re-select a user plane node that is closer to a wireless access network for the UE. When the UE accesses the home network or network in an enterprise through HeNB or HNB, and LIPA is executed, a user plane node closer to the HeNB/HNB can be selected or reselected for the UE, or a user plane node located in HeNB/HNB access network can be selected for the UE. The user plane mode can be core network equipment or a gateway. The SAE system can be a SGW, a PGW or an LGW. The UMTS system can be an SGSN or a Gateway GPRS Support Node (GGSN).
FIG. 2 is a structural schematic diagram of a Long Term Evolution (LTE) network deployment. As shown in FIG. 2, an MME 103 may be simultaneously connected to an R-10 HeNB 201 supporting LIPA, an R-11 HeNB 202 supporting LIPA, an HeNB 205 of different releases through HeNB GW 203, and an R-11 HeNB 204 supporting SIPTO or an R-10 HeNB (not depicted) supporting SIPTO. The R-10 and R-11 means numbers of releases regarding LTE standards defined by 3GPP.
FIG. 3 is a structural schematic diagram of an existing UMTS network deployment. As shown in FIG. 3, an SGSN 301 may be simultaneously connected to an R-10 HeNB 304 supporting LIPA, an R-11 HeNB 305 supporting LIPA and an R-11 HeNB 306 supporting SIPTO through an HNB GW 303.
LIPA in 3GPP R-10 does not support mobility. When the UE moves out of an HeNB supporting LIPA, the services of the UE related to LIPA are interrupted. It is required to support mobility in 3GPP R-11, and when the UE moves out of an existing HeNB or SIPTO HeNB, as long as the UE is still within a network in enterprise or a home network, a LIPA/SIPTO service of the UE should not be interrupted.
However, the network side is not able to determine whether the current service of the UE is LIPA or SIPTO. When the UE's subscription information supports both SIPTO and LIPA, the network side cannot determine whether the current service is LIPA or SIPTO based on the UE context information and subscription information because they both use general APN information. Therefore, when an R-10 HeNB, an R-11 HeNB, an R-10 SIPTO HeNB and an R-11 SIPTO HeNB are simultaneously connected, and when the UE moves out of the current base station, the network side cannot determine a subsequent action, such as, for example, keeping a LIPA/SIPTO service of the UE, or interrupting a LIPA/SIPTO service of the UE. Therefore, when the UE moves from an R-10 HeNB supporting LIPA to other cells, the network side may execute the wrong operation because the network side cannot correctly determine which kind of HeNB the UE is in, which will adversely affect the network.